1. Field of the Invention
The present invention relates to laminography and more particularly to a method and apparatus for reducing the blurring of the images obtained using an x-ray source with a traveling x-ray beam.
2. Description of the Related Art
U.S. Pat. No. 6,628,745, issued to the present applicant, describes a Laminography inspection system. As shown in FIGS. 1 and 2, an x-ray source 12 uses a narrow pencil beam 24 of high-energy electrons from a DC source of electrons 20 through a vacuum chamber 30 and directed to a linear target 22. A magnetic deflector 28 deflects the electron beam 24 so that it scans in an x-ray source line 52 along the linear target 22, as at 40, striking the target 22 continuously along the x-ray source line 52. An x-ray cone beam 16 is produced where the electron beam 24 strikes the target 22. This x-ray cone beam source 26 moves continuously to produce a moving cone beam 16 along the x-ray source line 52. The x-ray cone beam 16 exits the vacuum chamber 30 through a thin window located at the top of the vacuum chamber 30 just below a slit collimator 34. The collimator 34 produces a fan beam 32 from the cone beam 16. The fan beam 32 is directed to the object being inspected 2 in a direction transversely perpendicular to the direction of travel 4 of the object 2. X-rays passing through the object 2 are detected by a U-shaped or L-shaped linear detector array 14 in the plane 44 of the fan beam 32. The object 2 moves continuously on a conveyor 6 while the x-ray cone beam 16 scans from one end of the x-ray source line 52 to the other. This means that the object 2 is blurred transversely by the distance that the object 2 moves during the passage of the x-ray cone beam 16 from one end of the source line 52 to the other. For example, if the object moves 2 mm during the 800 mm travel of the x-ray cone beam, the blurring is 2 mm.
The application of the invention to CT systems is limited to the CT systems covered by U.S. patent application Ser. No. 10/630,364, incorporated herein by reference.